1. Field of the Invention
The present invention relates to a novel nitrogen semiconductor compound and a device fabricated using the semiconductor compound. More particularly, the present invention relates to a nitrogen compound simultaneously including groups with different electrical properties, i.e. at least one electron acceptor and at least one electron donor, in side chains of the compound, and a device fabricated using the nitrogen compound as an organic semiconductor material or a hole conducting material.
2. Description of the Related Art
Thin film transistors (TFTs) are representative devices fabricated using organic semiconductor compounds, and are generally composed of a substrate, a gate electrode, an insulating layer, source/drain electrodes, and a channel layer. Inorganic semiconductor materials, such as silicon (Si), have been commonly used as materials for channel layers of TFTs. However, with increasing demand for the manufacture of large-area, flexible displays at reduced costs, organic semiconductor materials are currently used as materials for channel layers, i.e. semiconductor layers, rather than inorganic semiconductor materials involving high costs and requiring high-temperature vacuum processes. Recently, studies on organic semiconductor materials for channel layers of OTFTs have been undertaken and the characteristics of the devices have been reported. Of these, a great deal of research is currently concentrated on low molecular weight and oligomer organic semiconductor materials, e.g., melocyanines, phthalocyanines, perylenes, pentacenes, C60, thiophene oligomers, and the like. Lucent Technologies Inc. and 3M Inc. have developed devices with charge carrier mobilities as high as 3.2-5.0 cm2/Vs using a pentacene single crystal (Mat. Res. Soc. Symp. Proc. 2003, Vol. 771, L6.5.1˜L6.5.11). In addition, CNRS, France, reported a device having a relatively high charge carrier mobility of 0.01˜0.1 cm2/Vs and a relatively high on/off current ratio (Ion/Ioff ratio) using an oligothiophene derivative (J. Am. Chem. Soc., 1993, Vol. 115, pp. 8716-8721). However, since these materials are largely dependent on vacuum processes in order to form thin films, the fabrication of devices incurs considerable costs. Under such circumstances, research is underway on organic polymer semiconductor compounds that can be coated by spin coating.
On the other hand, as other devices where organic semiconductor materials are used, there are exemplified organic solar cells. General solar photovoltaic cells consist essentially of a semiconductor layer and electrodes. The operational principle of a solar photovoltaic cell is as follows. Externally incident light generates electrons and holes inside a semiconductor layer. The electrons and holes migrate toward positive (P) and negative (N) electrodes, respectively, to generate a potential difference between the two electrodes. When load is applied to the solar photovoltaic cell, electric current flows in the solar photovoltaic cell. As described above, there is a growing tendency to use organic semiconductor materials as materials for semiconductor layers of solar photovoltaic cells rather than inorganic semiconductor materials involving high costs and requiring high-temperature vacuum processes. Thus, there is a need to develop a semiconductor compound that can be applied to the fabrication of devices, particularly, solar photovoltaic cells, by spin coating without a reduction in the efficiency of the devices despite increasing light intensity.